1. Field of the Invention
The invention relates to a communicating apparatus such as a facsimile apparatus or the like.
2. Related Background Art
In the case of receiving an image by a facsimile apparatus according to Recommendation T.30, an RTC pattern is detected in a non-ECM procedure or an RCP frame is detected in an ECM procedure, thereby completing reception of the image of one page, and the processing routine advances to a post-procedure.
However, in the case where noises are applied to a position of the RTC pattern or the RCP frame at a rear edge of the image or in the case where a modem diverges (or malfunctions) and a signal cannot be normally demodulated, since the RTC pattern or the RCP frame cannot be detected, there is a case where a receiver cannot advance to the post-procedure, only a transmitter advances to the post-procedure, and a communication error occurs.
To avoid such a communication error, in the conventional techniques, while an image is received in a high-speed mode such as V.17 or the like, a carrier of low-speed V.21ch2 modulation which is used in a procedure signal is monitored and when the carrier of the low-speed V.21ch2 modulation is detected, it is determined that the transmitter has advanced to the post-procedure, the image reception is finished, the mode is switched to a low-speed mode, and the procedure signal is received. With respect to a communicating procedure of the facsimile apparatus, transmission and reception of the procedure are made by V.21ch2 not by V.21ch1.
However, in the foregoing conventional technique, since QAM (Quadrature Amplitude Modulation) is used in the high-speed mode which is used for image transmission such as V.17 or the like, a frequency band which it occupies is wide and the same frequency component as the carrier of the V.21ch2 modulation is also included in signal components thereof.
There is, consequently, a problem such that it is difficult to certainly detect the carrier of the V.21ch2 modulation and it is possible that the communication error occurs adversely in a state where while the image signal is normally received, it is erroneously recognized that the carrier of the V.21ch2 modulation has been received and the mode advances to the low-speed mode.